This invention relates generally to an electrostatographic copier or printer, and more particularly, concerns a cleaning apparatus. In an electrophotographic application such as xerography, a charge retentive surface (i.e., photoconductor, photoreceptor or imaging surface) is electrostatically charged, and exposed to a light pattern of an original image to be reproduced to selectively discharge the surface in accordance therewith. The resulting pattern of charged and discharged areas on that surface form an electrostatic charge pattern (an electrostatic latent image) conforming to the original image. The latent image is developed by contacting it with a finely divided electrostatically attractable powder referred to as "toner". Toner is held on the image areas by the electrostatic charge on the surface. Thus, a toner image is produced in conformity with a light image of the original being reproduced. The toner image may then be transferred to a substrate (e.g., paper), and the image affixed thereto to form a permanent record of the image to be reproduced. Subsequent to development, excess toner left on the charge retentive surface is cleaned from the surface. The process is well known, and useful for light lens copying from an original, and printing applications from electronically generated or stored originals, where a charge surface may be imagewise discharged in a variety of ways. Ion projection devices where a charge is imagewise deposited on a charge retentive substrate operates similarly.
Although a preponderance of the toner forming the image is transferred to the paper during transfer, some toner invariably remains on the charge retentive surface, it being held thereto by relatively high electrostatic and/or mechanical forces. Additionally, paper fibers, Kaolin and other debris have a tendency to be attracted to the charge retentive surface. It is essential for optimum operation that the toner remaining on the surface be cleaned thoroughly therefrom.
A commercially successful mode of cleaning employed on automatic xerographic devices utilizes a brush with soft conductive fiber bristles or with insulative soft bristles which have suitable triboelectric characteristics. While the bristles are soft for the insulative brush, they provide sufficient mechanical force to dislodge residual toner particles from the charge retentive surface. In the case of the conductive brush, the brush is usually electrically biased to provide an electrostatic force for toner detachment from the charge retentive surface. Toner particles adhere to the fibers (i.e. bristles) of the brush after the charge retentive surface has been cleaned. The process of removing toner from these types of cleaner brushes can be accomplished in many ways. Typically, brush cleaners, use flicker bars to provide the detoning function.
Problems that can be associated with flicker bar detoning include: 1) damage to the cleaner brush as a result of the high impact forces at the point of contact, resulting in shorter brush lives [It has been shown that the brush life is dependent on the radius of curvature of an interfering surface. This reduced brush life with smaller radius interfering surfaces was due to an increase in brush radial shrinkage caused by an increase in permanent fiber deformation (also referred to as "fiber set") and an increase in fiber entanglement. It follows, therefore, that interfering with a surface of infinite radius (i.e. a flat surface) would provide the longest brush life.]; and, 2) higher cleaner unit manufacturing cost (UMC) due to periodic replacement or cleaning of the flicker bars.
Typically, rotary brush cleaners also encounter problems with photoreceptor filming and abrasion, and toner emissions. The filming and abrasion is due to the high impact forces that result when the brush fibers strike the toner and photoreceptor. Toner emissions usually result from inadequate or non-uniform air flow entering the cleaner at the housing to photoreceptor gaps.
The following disclosures may be relevant to various aspects of the present invention and may be briefly summarized as follows:
U.S. Pat. No. 5,138,378 to MacDonald et al. discloses a cleaning apparatus for detoning cleaner brushes. The brushes beat against the flicker bars for the release of toner carried by the brushes and for effecting suitable tribo charging of the brush fibers.
U.S. Pat. No. 5,132,730 to Hurwitch et al. discloses a cleaning apparatus for detoning cleaner brushes. The brushes beat against the flicker bars for the release of toner carried by the brushes and for effecting suitable tribo charging of the brush fibers.